Wood pulp screening vat



Sept. 2, 1941. y5.1; ORTON, JR 2,426,891

' woop PULP SCREENING VAT Filed Aug. 11, 1944 2 Sheets-Sheet'l s v55 gg abs 2 :inventor y6 OROTL 'J' @a s @Ww 7 v 'Ctttomeg Sept. 2, 194,7. s, T, oni-0N, JR 2,426,897

woon PULP SCREENING, vA'r I Filed Aug. 11, 1944 2 sheets-snee; 2

attorney wi'ness Herber' C Cove.

Patented Sept. 2, 1947 UNITED STATES* PATENT orrleca WOOD PULP SCREENING VAT Samuel T. Orton, Jr., Lunenburg, Mass., as-

signor to Union Machine Company, Fitchburg Mass., a corporation of Massachusetts l Application August 11, 1944, Serial No. 549,021

This invention relates to wood pulp screening vats, and more particularly to the construction of a vat carrying a plurality of screen plates held in place by clamping devices.

Wood pulp fibres are customarily screened to required sizes by passing the pulp over a set of screen plates having closely spaced, parallel, elongated slots therethrough. These screen plates form the vat bottom and are customarily arranged with the longest dimension extending substantially across the vat. In order to aid in the screening' process and to dislodge the pulp iibres which tend to clog the screen slots, a pulsating diaphragm has been customarily located beneath the plates and so operated that the downward movement of the water draws the pulp through theslotswhile the upward movement forces out the lodged bres. This water hammering action sets up a severe strain on the plates and their clamping devices; and it is imperative that the plates be held rigidly in position and provide a, water-tight seal with the vat structure. y It has been customary to secure the plates in place by means of dovetailed T shaped locking bars engaging bevelled edges on the plates, such as are shown in th'e patent to Witham, #678,082 of July 9, 1901. Since the plates must be readily removable ior cleaning and replacement, the locking bars have been clamped only at their ends by means of separate clamping devices or by screw threaded locking bolts.

The primary object of this-invention is to overcome these problems and to vprovide a very simple clamping device which will hold each plate in position under a uniform and adequate pressure throughout its entire extent.

A. further object is to hold a set of plates in place under an equalized pressure which may be readily adjusted and which will not change materially during use.

A further object is to provide a screen vat oi this general type with a clamping mechanism which, by a simple manipulation, may be caused to clamp all of the plates in position or alternatively release the same with a minimum of effort and waste of time on the part of the operator. Further objects will be apparent in the following disclosure.

Referring to the drawings which illustrate two embodiments of this invention:

Fig. 1 is a fragmentary longitudinal sectional view through a vat showing a set of interconnected, resiliently secured calmping devices holding the screen plates in position;

Fig. 2 is a similar view showing the positions of the parts when the plates are unclamped;

Fig. 3 is a fragmentary section taken substanmany on the une 3 3 of Fig. 1;

Various problems are inherent in such constructions. For example, the individually adjustable clamps and screws may not be tightened to the same degree, with the result that strains may be imposed on some of the screen plates 4 and others may not be tightly held. Also, the vibration of the vat and screens caused by the water hammering may result in the clamping devices working loose and permitting a screen plate to move and oversizeV libres to escape. It is important that the plates .be lheld tightly and under the same clamping pressure which may be readily adjusted. Also, since a considerable number of plates are assembled in a single vat, the separately adjustable screws and clamping devices have requirel aconsiderable wasteof time involved in disassembling the construction for removing and replacing the plates. Another problem has been found in the fact that the locking bar gradually changes shape under the hammering action of the water and buckles at its center with the result that the plate is not held under a uniform pressure throughout its length.

Fig. 4 isa transverse section ing bars which are in turn releasab'ly secured in position by means of a set of clamping devices. These devices are operated and fadjusted simultaneously by a pressure equalizing mechanism so arranged that the adjacent ends of the locking bars are held in place under substantially the same clamping pressure.

Referring to Figs. 1 to 4 inclusive, I have there y shown a vat, made preferablyof wood having end walls I0 and side walls Il arranged in a rectangular shape to provide both an open top and an open bottom. The bottom of 'the vat may be closed by a series of rubber diaphragms or the vat may be mounted on a further structure carrying the rubber diaphragms in accordance with standard practice. A'set of slotted screen through the which shows both an intermediate and an end;`

may be 1%" high. A suitable plate Size is 43"` by 12". Sets of parallel slots are cut crosswise of the plate through the thin portion between the ribs, which may be 4" long and arranged 4 to 8 slots to the inch. The slots are of the required width, such as from 0.006 to 0.085".

In the construction illustrated, each plate I2 is secured in position by means of a removable T-shaped locking bar 20 engaging one long side of the plate and holding the opposite bevelled side in locking engagement with a stationary dovetailedmetal bar 2l secured on a cross beam I6, as shown in Fig. 1. The locking bars 20 and dovetailed plates 2i alternate in arrangement throughout the tank with the screen plates therebetween. The locking bar 20, which may be shaped as shown in Fig. 6, has a dovetailed head-22 and a strengthening flange 23 depending centrally thereof. The dovetailed portion of the head 22 engages the mating wedge surface on the adjacent side of the plate and thus :forces the plate laterally against the similarly shaped wedging portion of the stationary bar 2|.

Each end of each -locking bar 20 is adjustably clamped in position against the beveled' edge of the screen pate I2 by means of a movable pressure device and preferably by means of a cam 25. The clamping force may be applied directly 'to the plate, but I prefer to use an intermediate cam follower 26. The latter is shown as a U-shaped metal clip (Fig. 3) which straddles a freely movable wooden clamp bar 21 extending substantially the full length of the side wall of the vat. The two depending ends of the clip 26 lie in contact with one end of the locking bar 20. A similar bar 21 is arranged on the opposite side of the vat to clamp down the other end of each locking bar 20. The wooden bar 21 may be provided with a longitudinal slot carrying a felt strip 28 (Fig. 3) which forms a water seal. Each bar 21 has a set of these U-shaped clips 26 arranged thereon in position to engage each locking bar 20. These clips extend below the wooden bar 21, so that each clip engages the lock bar directly, and the wooden part serves primarily -to support and locate the clips. The bar 21 is free to move but is held in position against the side wall II of the vat'by means of the bevelled surfaces 29 on the cams 25 engaging Amating bevels 30 on the U-shaped clips 26. That is, the clamping action not only forces each clip 26 downwardly but also causes it to hug closely against the side wall of the vat.

The movable cam 25 is Vpreferably mounted for rotation on a pivot pin 32. The pin is rotatably mounted in two spaced metal plates 33 and 34 which are fitted to close the opposite sides of an openingcut through the side wall II of the Y 'vat and arranged to provide space .for the cam zfoperating mechanism. The cam 25 is mounted "L: eccentrically so that' rotation of the cam serves Seither to clamp the clips 26 in position against the locking bars 20 (Fig. 1) or to release the same when the cam is rotated to the position of Fig. 2.

A primary feature of this invention lies in interconnecting the set of pressure devices which are arranged tohold the' movable locking bars 20 in place; and the interconnecting mechanism is so constructed and arranged that the locking bars are held under substantially the same equalized pressure. lTo this end, I provide an operating lever connected to each of a set of cams 25 on one side of the vat, and these levers are in turn moved by means of a single slide bar or rod 40. This rod is arranged to be moved by -a single pressure applying device such as a screw threaded bolt 42 suitably mounted on the vat wall. One slide bar 40 on each side of the tank is suilcient to operate the entire set of clamping devices. The outer plate 34 (Fig. 3) has a lug 44 through which the bolt 42 slidably passes. A nut 45 on the end of the bolt may be tightened down to draw the bolt upwardly. The lower end of the bolt carries a yoke 46, and the latter is pivotally connected to one end 41 of a bell crank lever mounted on a pivot 48 suitably supported on the wall plate 34. The outer end 49 of this bell crank lever is connected by a short link 50 pivotally attached to the intermediate portion of a link 52 formed of two spaced members. The upper end of the link 52 is pivotally connectedA to the slide rod 40. The lower end of the link 52 is connected pivotally to a rocking arm 54 on the shaft 32. The arm 54 is positioned between two collars 55 on the pin 32 that forms the pivotal mount of the cam 25. Thus by rocking the' lever arm 54 the cam 25 is moved to and from an -operative position where it clamps the clip 26 downwardly into locking engagement with the locking bar 20. The locking is accomplished by drawing the bolt 42 upwardly, which thus transmits the motion to the cam lever 54 and causes it to revolve toward the left "(Fig. 1) and thus swing the rst cam 25 toward the right.

Each of the intermediate cams 60 is mounted and arranged as shown at the central portion of Figs. I and 2 and the right hand part of Fig. 4. In this construction, the pivot pin 6I is mounted the same as the pin 32 shown in Fig. 3 on the two side plates 33 and 34. A lever arm 62 is keyedA or otherwise secured to the pin 6I and serves to rock the cam. The upper end of this lever has rounded surfaces, the left hand side being arranged, as shown in Fig. 1, to be moved by a collar 63 suitably secured on the slide rod 40 and the opposite side of. this lever engages a spring 64 which is located between the lever and a further eollar 65 secured on the rod 40. It will now be appreciated that when the bolt 42 is drawn upwardly the linkages shown at the left hand side of Fig. 1 will move the rod'40 towards the left.` This causes the spring '64 to crowd against the lever 62 and thus swing the cam 60 towards the right and force it downwardly into full locking engagement against the clip 26 that ls'located on that particular portion of the locking bar 21. A duplicate structure is arranged for each one of the intermediate locking bars 20. 'Thus it will be seen that when the rod 40 is moved toward the left by the screw bolt 42, the ends of the locking bars 20 on the same side of the vat will be held against the associated ends of the screen plates under an equalized pressure. Each rod 40 is separately adjusted.

The structure at the right hand4 side of Figs. 1 and 2 shows how the cam may be operated when close to the end wall of the vat. That is,

the arm 86 corresponding with the arm 82 at the intermediate portions of the vat, is made of such a length, or the cam is so positioned as to permit the arm 66 to be pivotally connected with a further link 81 which is inturn pivotally' mounted on a pin 38 passing through the two plates 33 and 34. The upper end of this rocking iever`61 is shaped and positioned so that it may be likewise moved by the collar 83 and the spring 84 so that the endwise movement of the rod 48 to the left causes the cam B8, similar to the other cams, to move towards the left and thus clamp down the associated end of the locking mar 28.

It has been found that the locking bar 28, although made with a strong reinforcing rib 23, as shown in Fig. 6, tends to become bowed under the high pressure involved as well as the vibration set up by the screening operation. so that the central portion of the screen may buckle or become loose. `To hold that central part of the screen plate in place, I make the dovetailed head 22 of the bar 28 slightly bowed downwardly so that the two ends of thebar are a little higher than the intermediate portion. Thus, when the two upwardly bowed ends are .forced down by thecams and associated clips 26, this pressure tends to force the intermediate portion i Vtowards the left. This force is transmitted of the bar 28 very tightly against the plate and l produces constant pressure by virtue of the bar being under stress. However, over longperiods intercrystalline fatigue of the metal reduces the elasticity and hence developed pressure, and I have provided a further construction in which the locking bar 2l) is provided with an enlarged portion 10 (Fig. 6) near its center'which provides sufficient metal for a bolt 12 to pass vertlcally through the bar. At this point the cross beam I5 of the vat which is cut away, as shown in Fig. 1, to provide for free movement of the downwardly depending flange 23 of the bar, is

further provided with a wall or plate having a hole 14 through which the bolt 12 freely fpasses. A threaded ilat headed nut 15 is inset int the bottom of the girt I5 and heldin place by screws. This serves to adjust the bolt 12 downwardly and draw the central portion of the locking bar 28 firmly into place against the adjacent edge of the screen plate. This reguires that when the locking bar 20 is to be removed, the lbolt 12 must likewise be taken from its position. It will also be observed thaty the end cross beams i4 are suitably cut out to permit inserting each locking bar into place, as shown in Fig. 1'.

A modified construction is shown in Fig. 5 wherein the slide rod 48 is omitted, and the different cams are connected by equalizing linkages. To this end, the link plates 52, above described, are connected to a draw link 18. Each of the intermediate cams has a short operating lever 18 which is pivotally connected at its top to a set of links 88. The right hand end of the draw link 18 is pivotally connected between the central portions of the links 80. The upper ends of the links 80 also pivotally carry the end of another draw link 82 corresponding with the link 18. vThat link 82 in turn connects to the The operation of the device will be apparent in view of the above description. In the construction of Figs. 1 and 2. when the draw bolt 42 is drawn upwardly the force is applied to move the links 52 towards the left and rod 48 will likewise go toward the left as soon as the iirst clamp 25 has moved into contact with its clip 26. Furthere movement of the drawv bolt 32 will force the rod 48 towards the left and cause the springs 84 to move the rocking levers 82 and 81 of the associated cams in such a direction as to. force the ends of the clamp bars into place. Thus the cams are moved together or substantially simultaneously. The pressure imposed by the draw bolt 42 is equalized by the interconnecting linkages and springs and each one of the clamping clips is held under substantially the same pressure against its associated locking bar 28. In the construction of Fig., 5, the same effect is produced when the draw bolt 42 is moved upwardly. This swings lthe bell crank lever 41, 49 in such a way as to move the floating linkage 52 through the draw links 18 and 82 to the rocking arms19 and 85 of the cams and moves all cams substantially at the same time into engagement with the locking bars. Whether one camO seats before another is immaterial, since the clamping forcels ultimately distributed equally. When vit is desired vto remove the plates, it is merely necessary to loosen the nut on the draw bolt 42, and the springs 84 (Fig. 1) will swing the cams back out of place. In the construction of Fig. 5, the operator may need to forcibly move one of the cams and thus cause all of the cams to swing out of locking engagement. It will be appreciated thatby adjustment of the two draw bolts 42 on the opposite sides of the vats all of the clamp bars may be held under equalized and substantially the same pressure at their opposite ends thereof.

It will now be appreciated that various mechanical equivalents may be substituted for the cams, linkages andA other constructions illustrated and above described. For example, a cam may be considered as an inclined plane which is found in screws, sliding cams and other constructions. Also, the operating linkages and the draw bolt 42 may be eliminated and the draw rod 48 extended through the vat wall I8 where it may be adjustably positioned by means of a nut. The primary feature of this invention involves moving such locking devices substantially simultaneously so that the ends of a set of clamp bars may be locked in place by the operation of a single mechanism and so that these bars may be held at those ends under a substantially equalized pressure. It will therefore be apparent that the above disclosure is to be considered as explaining the principles of my invention and illustrating a preferred embodiment thereof and not as imposing limitations on the claims appended hereto.

I claim:

1. A wood pulp screening vat comprising side walls and spaced cross beams. a set of screen plates mounted on the beams, removable locking bars clampingly engaging edge portions of said plates and securing them on said beams, pressure devices mounted on the vat and engaging the opposite ends of said bars. pressure equalizing mechanism connected to hold the pressure devices at the same ends of the bars in clamping engagement therewith under an equalized pressure, and means for forcing the mechanism into said pressure equalizing relationship.

2. Apparatus according to claim 1 comprising a separate device releasably securing the middle portion of a locking bar to a cross beam independently of the pressure equalizing mechanism.

3. A wood pulp screening vat comprising side walls and spaced cross beams, a set of screen plates mounted on the beams, removable locking bars clampingly engaging edge portions of said plates and securing them on the beams, a pressure device engaging each end of each bar, a resilient pressure equalizing mechanism mounted on aside wall and connecting the adjacent pressure devices which forces the latter under an equalized resilient pressure into holding engagement with the adjacent ends of the bars, and a releasable means connected to force said equalizing mechanism into said pressure equalizingand plate clamping relationship.

4. A wood pulp screening vat comprising side walls and spaced cross beams, a set of screen plates removably mounted on the beams, removable locking bars clampingly engaging edge porwall and individually securing the adjacent ends of the bars in plate locking positions, a pressure equalizing linkage mechanism mounted on a side wall and operatively inter-connecting the adjacent cam devices which releasably holds them under an equalized pressure against the bars, and manually operable means for adjustably securing .tions of the plates and securing them on said beams, cam devices movably mounted on a side cam holding rela- -each side wall, individual cams mounted on each side wall and movably engaging the adjacent followers, a pressure equalizing linkage mechanism mounted on each side wall and inter-connecting the adjacent cams for moving them under an equalized pressure, and a manually operable device for moving said equalizing mechanism and applying a releasable pressure therethrough to the cams to lock the plates in position.

SAMUEL.V T. ORTON, Ja.

REFERENCES CITED The following references are of record in the ille of this patent:

` UNITED STATES PATENTS Number Name Date 678,082 Witham July 9, 1901 859,228 Jentz July 9, 1907 2,128 ,439 Stinson Aug` 30, 1938 1,268,189 Vontell June 4, 1913 2,004,507 Moravec June 11, 1935 2,390,692 Clem et al Dec. 11, 1945 

